This invention relates to diaphragm actuated valves and in particular to solenoid operated diaphragm valves incorporating pilot valve actuation.
Diaphragm valves incorporating pilot valve actuation are well known in the art. In general, these valves include a flexible diaphragm interposed between the valve input and the valve output sides. The diaphragm generally includes an opening and higher pressure fluid from the valve input side is allowed to equalize the force acting on each side of the diaphragm. When the main valve is to be activated, a pilot valve is opened which quickly relieves pressure on a first side of the diaphragm, permitting the high pressure fluid on the second side of the diaphragm to lift the diaphragm, thereby opening the main fluid passageway through the valve.
It also is common to employ a solenoid to activate the pilot portion of the valve. The solenoid generally is operatively connected to the pilot valve so that energization of the solenoid opens the pilot valve while de-energization of the solenoid permits closure of the pilot valve. The pressure differential on opposite sides of the diaphragm caused by pressure relief through the pilot valve is used to lift the diaphragm.
In applications where the main inlet fluid pressure fluctuates over relatively wide ranges, solenoid operated diaphragm valves have been known to operate unsatisfactorily. Thus, at high input pressures, the rating of the solenoid may be insufficient to permit the solenoid to operate directly on the diaphragm to open the valve and failure of the solenoid results. While pilot operation of the diaphragm valve is intended to avoid solenoid burn out, at low input pressures, the differential on each side of the diaphragm may be insufficient to open the diaphragm, and flow through the valve becomes unpredictable.
One solution to these general prior art deficiencies is given in the U.S. Pat. No. to Rolfe, 3,208,716, issued Sept. 28, 1965. While the prior art in general, and Rolfe in particular, work well for their intended purposes, some applications require that a relatively high pressure be applied to the pilot valve in order to reduce pilot valve leakage. The application of the higher force to insure pilot valve closure often affects valve operation adversely. The valve disclosed hereinafter is an improvement over the prior art in that it provides positive diaphragm actuation, even at low pressure differentials, while it insures that the pilot valve positively seats.
One of the objects of this invention is to provide a low cost pilot actuated diaphragm valve.
Another object of this invention is to provide a pilot controlled diaphragm actuated valve in which the pilot valve has a positive force acting to close it.
Another object of this invention is to provide a valve construction wherein the force acting to close the pilot valve may be varied according to application use.
Other objects of this invention will be apparent to those skilled in the art in light of the following description and accompanying drawings.